Sensitive and specific quantification of human genomic deoxyribonucleic acid (DNA) in forensic science specimens: casework examples.

We describe the forensic science application of a method for quantification of human genomic deoxyribonucleic acid (DNA). The two cases cited in this report involve DNA samples extracted from skin tissue and bloodstained clothing recovered from different crime scenes. High-molecular-weight DNA was recovered from both specimens, and the concentrations of these DNAs were estimated to be approximately 0.5 microgram/microL by ethidium bromide/agarose gel electrophoresis. Using the human-specific DNA probe p17H8 (locus D17Z1) to quantify the amount of human genomic DNA in these samples, it is shown that less than 1% of the DNA isolated from the skin tissue is of human origin and that the DNA isolated from the bloodstained clothing is effectively devoid of human DNA sequences. These case examples illustrate the need to quantify not only the total amount of DNA recovered from forensic casework material, but also the proportion of the DNA that is of human origin.     

Applications of isoelectric focusing in forensic serology

The typing of certain polymorphic proteins present in human body fluids is an important aspect of the analysis of serological evidence. This is particularly true when dealing with evidence related to violent criminal activity such as homocide, assault, or rape. Until recently, the routine analysis of the genetic polymorphisms of interest relied upon conventional electrophoretic techniques such as horizontal starch or agarose slab gel or both, cellulose acetate, and vertical polyacrylamide gradient gel methods. These techniques adequately separate a limited number of common variants. In some cases, these methods are still those of choice. However, as a result of the nature of the conventional approach, problems with time required for analysis, resolution, diffusion of bands, sensitivity of protein detection, and cost are often encountered. Isoelectric focusing (IEF) offers an effective alternative to conventional electrophoresis for genetic marker typing. This method exploits the isoelectric point of allelic products rather than charge-to-mass ratio in a particular pH environment. The advantages of employing IEF include: reduction of time of analysis, increased resolution of protein bands, the possibility of subtyping existing phenotypes, increased sensitivity of detection, the counteraction of diffusion effects, and reduced cost per sample.     

A survey of the incidence of missing anterior teeth: potential value in bite mark analysis.

Bite mark analysis involves comparison of individual dental characteristics between a dentition and the bite injury. A bite mark injury may result from sexual assault, or physical assault, and defensive injuries, and as such can be used to link a suspect to a victim or vice versa. Missing teeth are one of the characteristics that could implicate or exclude a suspected biter. However frequency data for use by forensic odontologists can only be collated from epidemiological studies. Therefore an audit was undertaken of missing anterior teeth in adult patients (n = 1010) attending for treatment, gathering data that could be more relevant to odontology. One in five of the sample presented with missing teeth that were either replaced with a denture (11%), not replaced (6%) or missing with the gap closed (2%).     

Sexual asphyxia in siblings

We present an accidental autoerotic asphyxiation of a 24-year-old man. Further investigation revealed that 18 years earlier, his brother, then 13, had been found dead, hanging in the family bathroom. Although that death had been ruled a suicide, reevaluation of the death scene indicates that this was also an autoerotic asphyxiation. This is the first reported case of sexual asphyxia involving siblings.     

Analysis of N,N-diethyl-m-toluamide (DEET) in human postmortem specimens

N,N-diethyl-m-toluamide (DEET) levels in postmortem specimens of stomach and contents, blood, liver, and urine are reported following ingestion of the compound. DEET was analyzed by gas chromatography with an OV-101 column and a nitrogen phosphorus detector. The presence of the compound in the four postmortem specimens was confirmed by mass spectrometry.